Steel reinforced concrete structures suffer corrosion induced damage as the result of carbonation or chloride contamination of the concrete. The steel reinforcement corrodes to produce products that occupy a larger volume than the steel from which the products are derived. As a result expansion occurs around reinforcing steel bars. This causes cracking and delamination of the concrete cover to the steel. Repairs involve removing this patch of damaged concrete. It is good practice to remove the concrete (break it out) behind the corroding steel and to remove as much of the contaminated concrete as possible. The concrete profile is then restored with a compatible cementitious repair concrete or mortar. The concrete then consists of the parent concrete (remaining original concrete) and the repair material at the patch. Previous research effort has resulted in the generation of a number of competing high performance proprietary cementitious concretes or mortars for use as concrete repair materials.
The parent concrete adjacent to the repair area is likely to contain some aggressive contaminants as the result of its exposure to the environment that caused the damage at the patch. Sacrificial anode assemblies may be tied to the steel to provide galvanic protection to the steel that is in the adjacent parent concrete prior to covering the steel and restoring the concrete profile with the repair material. One example is shown in Repair Application Procedure number 8 published by the American Concrete Institute (ACI). The anode assembly typically comprises a pre-assembled anode and backfill wherein the backfill contains an activating agent and the assembly forms a rigid assembly that can be tied to the steel exposed in the cavity formed by the removal of the damaged concrete. One problem with this arrangement is that the current delivered to the steel in the adjacent concrete depends on the resistivity of the concrete repair material. Repair materials with a high resistance to the ingress of contaminants also tend to have a high electrical resistivity, but a high electrical resisitivity of the repair material reduces the current output of the anode and therefore the protection current delivered to the steel in the parent concrete adjacent to the repair. A proposed solution to this problem is to use a low resistivity bridging mortar to connect the preformed anode assembly tied to the steel to the original (parent) concrete prior to installing the concrete repair material. However this compromises the quality of the repair material and increases the number of interfaces between the sacrificial anode and the parent concrete where further problems may occur.